J. Partanen

Aging and spectral analysis of EEG in normal subjects: a link to memory and CSF AChE.

We studied the effect of aging on EEG spectra recorded from T5–O1 (T6‐O2) derivation. The aging series composed of 52 normal individuals aged 20 to 91 years. Seventy‐nine per cent of visual and 81% of quantitative EEGs were considered normal. The absolute amplitude of delta and theta bands and absolute power of delta band were lower for the oldest group (aged 60 and over) than for the youngest group (aged 20–39 years). Age was inversely related to the amount of delta and theta indicating that the amount of slow activity in quantitative EEG does not increase with age in the context of good health status. Women had more beta activity compared with men. In addition, the amount of beta and alpha bands showed tendency for a reduction with age. Fifteen subjects aged 50 years or older participated in a 2‐year follow‐up including EEG and neuropsychological evaluation. Seven of them deteriorated in learning ability and showed increase in delta activity. In the oldest age group, delta amplitude was positively correlated with intrusion errors in the list learning test and inversely related to acetylcholinesterase activity of the CSF. Thus, a link between the cholinergic system, EEG slowing and memory problems in old age is suggested.

Slowing of electroencephalogram and choline acetyltransferase activity in post mortem frontal cortex in definite alzheimer's disease

Twenty-five (96%) of 26 patients with histologically verified moderate to severe Alzheimers disease had abnormal electroencephalograms. The patients with the slowest (5-6 Hz) dominant occipital rhythms had significantly lower choline acetyltransferase activity in the post mortem frontal cortex than the patients with highest rhythm (8-9 Hz) (analysis of covariance adjusted for the neuropsychological test score). Concentrations of dopamine, noradrenaline or serotonin in the frontal cortex did not differ in the patient groups with the slowest and highest rhythms. Neither did scores of senile plaques or neurofibrillary tangles differ between these groups. In Alzheimer patients, the frequency of the dominant occipital rhythm correlated with the total score of the neuropsychological test (r = 0.58, P less than 0.01) and with the subscales of praxic functions and expressive speech, memory and general reasoning. The results suggest that the cholinergic deficit may contribute to the slowing of the electroencephalogram found in patients with Alzheimers disease.

Changes in absolute power values of EEG spectra in the follow‐up of Alzheimer's disease

We have studied the absolute and relative power and amplitude of EEG spectra (T6–02) of 24 patients with “probable” Alzheimers disease at the early stage of the disease and 1 year later and also compared the values to those of normal elderly controls. A remarkable variability of the absolute values was evident both for the patients and for the controls. The AD patients had significantly higher absolute theta amplitude and power and the absolute beta values tended to decrease compared to controls. Absolute delta and alpha values did not differ from those of the controls. The relative delta, theta and alpha power and amplitude, and beta amplitude showed significant changes in AD patients, whereas the relative beta power was unchanged. In the follow‐up of AD patients at 1 year, absolute alpha values decreased and delta values tended to increase. As to relative values, both the alpha and the delta significantly changed but the theta and the beta were unaltered. We conclude that both absolute and relative power and amplitude values should be considered in EEG studies of dementia patients. Absolute values are especially useful in follow‐up.

The effects of concurrent manipulations of cholinergic and noradrenergic systems on neocortical EEG and spatial learning

In the spatial learning test, young animals were divided into three groups receiving saline, scopolamine (0.15 mg/kg), or scopolamine (0.8 mg/kg). Half of the animals in each group were lesioned with DSP-4 to destroy noradrenergic fibers. DSP-4 lesions did not produce any significant impairment alone or in combination with a lower dose of scopolamine (0.15 mg/kg), but they did further augment the scopolamine (0.8 mg/kg)-induced defect. In the electroencephalography (EEG) experiment, both control rats and DSP-4-lesioned rats were recorded after receiving saline, scopolamine (0.15 mg/kg), and scopolamine (0.8 mg/kg) injections. Scopolamine induced a dose- and behavioral state-dependent EEG slowing, whereas DSP-4 lesions did not change either baseline EEG activity or EEG reactivity to scopolamine.

Brain cholinergic enzymes and cortical EEG activity in young and old rats.

1. Cholinergic enzymes (ChAT, AChE) in different areas of the brain and cortical electroencephalography (EEG) activity were investigated in young and old rats. 2. In old rats, ChAT activity was low in the striatum, but high in the amygdala. Compared to young rats, ChAT activity in old rats was unchanged in the frontal, parietal/occipital and entorhinal cortex as well as in the hypothalamus, midbrain, hippocampus and brain stem. 3. AChE activity in old rats was lower than in young animals in the parietal/occipital cortex, hippocampus, striatum and brainstem. In other areas of the brain AChE activity was unchanged. 4. In old rats the peak frequency (Fp) of cortical EEG activity (mobility-related) was significantly lower than in young animals, both frontally and occipitally. The power of 5-10 Hz frequency band was markedly lower than in young rats. During immobility, the power of the 1.5-3 Hz and 3-5 Hz bands was lower in the frontal cortex of old rats. The power of 3-5 Hz, 5-10 Hz and 10-20 Hz bands was lower in the occipital cortex of old rats. In all of the old rats, but not in any of the young ones, symmetric high voltage activity was observed in the frontal pole of the cortex. 5. These results suggest that the age-related decrease of higher frequencies of cortical EEG activity may be related to the decrease of AChE activity in the parietal/occipital cortex. This decrease in AChE may reflect degeneration of the cholinergic synapses.

Taurine in normal and diseased human skeletal muscle

Taurine content of 199 clinical muscle biopsies was determined and correlated to histometric data of 121 cases. Taurine concentration in muscles was markedly dependent on fiber type distribution, taurine being more abundant in the slow, oxidative type 1 fibers than in the type 2 fibers. Taurine concentration rose slightly with age and tended to be higher in denervations, muscular dystrophies and myotonias, but the differences from the control values were non‐significant.

Effect of Vigabatrin on the Electroencephalogram in Rats

Summary: Vigabatrin (γ‐vinyl GABA; GVG) is a new antiepileptic drug (AED) that increases the level of the inhibitory transmitter, γ‐aminobutyric acid (GABA) in the brain. We evaluated the effect of GVG on the EEG of normal rats. GVG was administered intraperitoneally (i.p.) at a dose of 100 mg/kg once a day for 12 days. EEG was recorded at baseline, on the fourth day, at the end of the 12‐day GVG period and 10 days after discontinuation of GVG. GVG increased the amplitude of delta (1–4 Hz) and theta (4–8 Hz) frequency bands and resulted in slowing of the peak frequency (F) and mean frequency (Fp) in both the frontal and occipital cortex, especially during waking‐immobility. EEG changes normalized within 10 days after the last GVG injections. The results suggest that a relationship may exist between the EEG changes and increase in GABA levels with GVG.

Tetrahydroaminoacridine improves the recency effect in Alzheimer's disease

We investigated the effects of a single administration of tetrahydroaminoacridine (25 and 50 mg, orally), a cholinesterase inhibitor, on memory function in Alzheimers disease patients. The recall of memory items from the end of the word list (recency effect) was improved in a subgroup of Alzheimers disease patients (responders 10 out of 28) by tetrahydroaminoacridine 50 mg. However, tetrahydroaminoacridine 50 mg had no effect on the recall of those words from the beginning or middle of the list. Tetrahydroaminoacridine did not markedly improve non-verbal delayed matching to sample or paired associates learning in any of the Alzheimers disease patients. The responders performed better than the non-responders in tests measuring memory and frontal functions. The responders had less severe hippocampal atrophy and less prefrontal blood flow defect, and had a lower frequency of the apolipoprotein E4 allele than the non-responders. These results suggest that acute tetrahydroaminoacridine treatment may stimulate the recency effect, and that a severe dysfunction of hippocampus and prefrontal regions blocks this effect of tetrahydroaminoacridine on short-term memory performance.

Amino acid levels in cerebrospinal fluid of rats after administration of pentylenetetrazol

1. We studied the effect of pentylenetetrazol (PTZ)-induced myoclonic jerks and generalized clonic-tonic convulsions (GC) on the levels of neurotransmitter amino acids in the cisternal CSF of rats. 2. The levels of aspartate, glutamate, glycine, and taurine were elevated in the CSF during myoclonic jerks and more distinctly immediately after GC. 3. During the recovery period of postictal depression seen in EEG (5 min after GC), the CSF levels of transmitter amino acids were lower than in the control group. 4. PTZ-induced irritative activity in the EEG disappeared in 24 hr but the levels of amino acids remained abnormal. 5. Amino acid changes in the CSF following PTZ-induced convulsions might indicate that the release of amino acids into the extracellular space is increased before and during the propagation of PTZ-induced seizure and decreased during postictal depression.

EEG reactivity correlates with neuropsychological test scores in Down's syndrome

Introduction – Downs syndrome patients express a neurodegenerative disorder and mental retardation. We studied the reactivity of EEG and its correlation with neuropsychological test score in Downs syndrome. Material and methods – We studied 32 patients with Downs syndrome and 31 controls for blocking of occipital EEG activity. The temporo‐occipital EEG with eyes open (EO) was compared with resting EEG with eyes closed (EC), (EC/EO ratio). Results – Both Down patients and controls showed significant diminution of alpha, beta and theta activity and decrease of EEG frequency with EO. However, there was a significant impairment in Down patients in the EC/EO ratio in alpha band, compared to controls. The controls had no correlation of the alpha EC/EO ratio with age or gender. The Down patients showed a significant correlation of this variable with age which is in accordance with a gradually progressing disease. They had also significant correlations of the alpha EC/EO ratio and neuropsychological test scores which indicates that this ratio may be a more general measure of cerebral or hemispherical dysfunction than a mere impairment of visual activation. Down patients also showed significant differences in resting EEG variables, compared to the controls, even if the conventional EEG showed normal or mildly slowed dominant occipital rhythm in most of the patients. The correlation analysis between resting EEG and EC/EO ratio variables pointed out that they are relatively independent, representing different factors in the regulation of EEG. Conclusions – We believe that the alpha EC/EO ratio of EEG add a new domain in the assessment of cerebral dysfunction in Downs syndrome.